Atmospheric lead pollution history during four millennia (2000 BC to 2000 AD) in Sweden

This paper discusses the history of atmospheric lead pollution, the past ge ographic distribution of atmospheric lead deposition in Sweden, and the fat e of the pollution lead in boreal forest soils. The paper is based on analy ses of Pb-206/Pb-207 isotope ratios and lead concentrations in lake sedimen ts, peat deposits and soil profiles from Sweden. The first signs of atmosph eric lead pollution date back to 3500 to 4000 years ago. There was a small, but clear peak during the Greek-Roman period around 0 AD. About 1000 AD a major and unreversed increase occurred; varved lake sediments disclose poll ution peaks at about 1200 AD and 1530 AD, which match peaks in metallurgy i n Europe. With the Industrial Revolution atmospheric lead pollution increas ed, however, not as much as usually suggested, and not at all from what can be called background values. Lead pollution increased markedly after World War II, peaked about 1970, and will, if the present trend continues, soon be back to Medieval levels. The distribution of pre-industrial pollution wa s similar to the contemporary pattern with a strong south to north gradient , as a result of northward atmospheric transport from continental Europe an d the British Isles. The cumulative load of pollution lead through time is 2 to 3 g m(-2) in S Sweden, and of this load at least 50% was deposited pri or to 1800 AD. In boreal forest soils, the main part of this pollution lead has accumulated in the B horizon. Present-day concentrations in the mor la yer are up to 1000 times higher than in the pristine forest prior to pollut ion.